1. Field of the Invention
The invention relates to a carrier substance of an inorganic molecular structure and provided with a surface coating produced by application of a substance and heat treatment. Furthermore, the invention relates to a method of producing, as well as suitable uses for, the surface coating.
2. The Prior Art
For providing a scratch and temperature resistant surface, it is generally known to use surfaces of enamel, glass, glass ceramics or similarly structured systems, i.e. networks particularly of silicon dioxide and/or other metal oxides. Also, metal surfaces such as, for instance, steel, stainless steel, aluminum, and chromium, which while inferior as regards these properties, are, nevertheless, acceptable compared to surfaces of organic materials. The above mentioned properties are especially needed in surfaces used in the field of household appliances.
Also, surfaces coated with polytetrafluoroethylene (Teflon(copyright)) or silicone are known which are distinguished by their non-stick properties. The excellent non-stick properties of PTFE and silicone-like surface systems against burnt-in food are particularly noticeable in baking pans, cooking and baking utensils. However, since those coatings are relatively thick their maximum useful temperatures are below 250xc2x0 C. to 300xc2x0 C. Moreover, because of its relatively thick coating such a surface will suffer significant damage when used frequently and abusively, and will lose its favorable charateristics in those areas which have been damaged. A further disadvantage of the known surface coating is that bonding agents have to be applied to a scratch and temperature resistant surface prior to the application of the organic coating. While non-sticking is the resultant new property, the scratch and temperature resistance of the surface of the carrier material will be lost. While in its new state a non-stick surface requires no scrubbing or scouring to be cleaned, its non-stick properties will deteriorate after several uses particularly close to their maximum useful temperature, and cleaning is possible only with greater effort. The surface will thus be damaged mechanically, and the non-stick property of the surface will deteriorate.
Bonding with water or oil based materials or with water/oil emulsions is accomplished by bonding forces between molecular groups of the surface and corresponding atoms/molecules of the bonded organic material. Typical reactive molecular groups of the surface are, for instance, OH groups which to a great extent define the surfaces of silicone based systems. The OH groups at the carrier surface are either absorbed by bonding the coating, or they escape from the system as a result of chemical reaction. The remaining few reactive molecular groups of the coating material then define the non-stick characteristics. A substantial draw back is that such relatively thick surface coating behaves very much like organic materials of low scratch and temperature resistance. The properties of the underlying inorganic layer cannot permeate to the outer surface.
It is, therefore, an object of the invention to provide a surface on metallic, ceramic and glass-like carrier materials with non-stick properties against water and/or oil based organic materials or water/oil emulsions while at the same time being substantially more temperature and scratch resistant than conventional coatings of PTFE or silicone.
In accordance with the invention the object is accomplished by a carrier material and a surface coating in which the surface coating in its uppermost molecular layers consists of a compound of inorganic molecules of the carrier material and organic molecules of an applied substance. In another advantageous embodiment, the invention proposes a novel method of producing a non-stick surface on a base carrier surface by applying to the surface an organic substance including silicone-like networks followed by a heat treatment for cross-linking the molecules of the carrier surface and of the substance and removing, by evaporation, any excess substance whereby a new network is formed of surface and substance molecules. Other objects will in part be obvious and will in part appear hereinafter.
Aside from a scratch and temperature resistant surface the advantages attainable by the invention are, in particular, that the surface is resistant even against temperatures in excess of 300xc2x0 C. and that it has non-stick properties with respect to water and/or oil based organic materials or water/oil emulsions. On a molecular plane the surface of the substrate has at least local network structures with at least one layer of molecules of reactive bonding molecular groups being bonded to the uppermost network plane. A layer-forming organic substance with silicone-like networks is applied to this surface. In the upper molecular layer of the substrate surface close to the surface the reactive bonding molecular groups react chemically with the molecules of the organic substance and form a transitional range with respect to the organic surface without leading to the formation of a pure organic layer. Within this transitional range the reacting molecular groups are substituted by hydrophobic and/or oleophobic atoms or molecules or groups of molecules. If the non-stick coating does not reject another surface when in use, the latter surface will define the surface characteristics of the entire system. In accordance with a further embodiment unintended organic protective films on the non-stick surface can be removed without loss of the non-stick properties. Except in the mentioned transitional range between inorganic and organic substances the growth of an organic layer is prevented at the end of or during a heat treatment process above the decomposition temperature of the silicone-like substance. As a result, the organically modified uppermost plane of the inorganic substrate remains. An advantageous field of application of surfaces modified in this manner relates to enameled surfaces of substrates. The modified surface is used especially in connection with electrical household appliances or kitchen furniture. The use of a modified surface imparts especially advantageous properties to a glass-ceramic cooking surface, baking, roasting, broiling and/or microwave oven and/or to components to be placed into a roasting chamber and/or to baking, roasting, cooking containers, for instance, cooked food containers.